From patchwork Wed Jun 24 09:29:10 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Daniel Vetter X-Patchwork-Id: 11622727 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 16CC66C1 for ; Wed, 24 Jun 2020 09:29:20 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E500A20857 for ; Wed, 24 Jun 2020 09:29:19 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=ffwll.ch header.i=@ffwll.ch header.b="OarMyjw8" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2389192AbgFXJ3T (ORCPT ); Wed, 24 Jun 2020 05:29:19 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60722 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2388671AbgFXJ3T (ORCPT ); Wed, 24 Jun 2020 05:29:19 -0400 Received: from mail-wr1-x441.google.com (mail-wr1-x441.google.com [IPv6:2a00:1450:4864:20::441]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A5784C061573 for ; Wed, 24 Jun 2020 02:29:17 -0700 (PDT) Received: by mail-wr1-x441.google.com with SMTP id s10so1529612wrw.12 for ; Wed, 24 Jun 2020 02:29:17 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ffwll.ch; s=google; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=W0wVhEMhWH3hYon0OeouApnRcgkILMJ/Xt7oWX7gLsg=; b=OarMyjw89XIpDvY/QrTzsO6Ols2ILfTaOBq04SQiR+FuIsZe012LrnZ7cB4zo7Vdxw mQrHMwiF33CoS+wnoev+YLG6RDjnn2k2B+S00boaApeE/hk1EY3pTXyPCTpC4VkZJi9h JHGgzLTawQgb5CcaWIZu3lOSxK1uE6W8rGlRo= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=W0wVhEMhWH3hYon0OeouApnRcgkILMJ/Xt7oWX7gLsg=; b=Ahd+zhv6hYoaqk0IbxSTZSx+ctulCTYCDYONeMRacErrmKejJMs1ddYo6Tw1FFK74f zYa5+GpTfzGnMYjfXEaAiQLxn/rJp5CRoHUL4/RG6RKnALSqB+rs0KIL1jgzpiopv0+k h+mFUXwSXWBhIxjoh29hPggOgtBHjljIoLHUd7d6ssLq9xlXM7yTXvpm6EYQ/B4fZsqN hxGkna3hW+n1veSFZjfJDKvl6BeK7Ime1oTClRCvLIKdW+tyU18bdkse47Fcs2deC3I8 rVVXFnt5NfZHCboarxqSBE6kWw5aEkWs66qQlsSrXqYwSuU3nes8ZB2DMtw6IOoPZyWN mGnQ== X-Gm-Message-State: AOAM533omPV+tDq0wLkczfwcU/4dySkF7WxfNl0i4otwV4UHMy/iflPV ljqKeHQPxlHMeqLVfdvpXjlokA== X-Google-Smtp-Source: ABdhPJzW8mAFVy2khktm0xHnYGgLgpNPmVkDKLcdGO6ITsJNOwZiUyPwYV1adoRJGMo/aW8PBK8RYQ== X-Received: by 2002:adf:a34d:: with SMTP id d13mr28876302wrb.270.1592990956247; Wed, 24 Jun 2020 02:29:16 -0700 (PDT) Received: from phenom.ffwll.local ([2a02:168:57f4:0:efd0:b9e5:5ae6:c2fa]) by smtp.gmail.com with ESMTPSA id l190sm7212565wml.12.2020.06.24.02.29.14 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 24 Jun 2020 02:29:15 -0700 (PDT) From: Daniel Vetter To: DRI Development Cc: Daniel Vetter , shlomo@fastmail.com, =?utf-8?q?M?= =?utf-8?q?ichel_D=C3=A4nzer?= , =?utf-8?q?Noralf_Tr?= =?utf-8?q?=C3=B8nnes?= , Thomas Zimmermann , Daniel Vetter , Maarten Lankhorst , Maxime Ripard , David Airlie , Daniel Vetter , stable@vger.kernel.org, Bartlomiej Zolnierkiewicz , Geert Uytterhoeven , Nathan Chancellor , Qiujun Huang , Peter Rosin , linux-fbdev@vger.kernel.org Subject: [PATCH] drm/fb-helper: Fix vt restore Date: Wed, 24 Jun 2020 11:29:10 +0200 Message-Id: <20200624092910.3280448-1-daniel.vetter@ffwll.ch> X-Mailer: git-send-email 2.27.0 In-Reply-To: <20200623155456.3092836-1-daniel.vetter@ffwll.ch> References: <20200623155456.3092836-1-daniel.vetter@ffwll.ch> MIME-Version: 1.0 Sender: linux-fbdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fbdev@vger.kernel.org In the past we had a pile of hacks to orchestrate access between fbdev emulation and native kms clients. We've tried to streamline this, by always preferring the kms side above fbdev calls when a drm master exists, because drm master controls access to the display resources. Unfortunately this breaks existing userspace, specifically Xorg. When exiting Xorg first restores the console to text mode using the KDSET ioctl on the vt. This does nothing, because a drm master is still around. Then it drops the drm master status, which again does nothing, because logind is keeping additional drm fd open to be able to orchestrate vt switches. In the past this is the point where fbdev was restored, as part of the ->lastclose hook on the drm side. Now to fix this regression we don't want to go back to letting fbdev restore things whenever it feels like, or to the pile of hacks we've had before. Instead try and go with a minimal exception to make the KDSET case work again, and nothing else. This means that if userspace does a KDSET call when switching between graphical compositors, there will be some flickering with fbcon showing up for a bit. But a) that's not a regression and b) userspace can fix it by improving the vt switching dance - logind should have all the information it needs. While pondering all this I'm also wondering wheter we should have a SWITCH_MASTER ioctl to allow race-free master status handover. But that's for another day. v2: Somehow forgot to cc all the fbdev people. Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=208179 Cc: shlomo@fastmail.com Reported-and-Tested-by: shlomo@fastmail.com Cc: Michel Dänzer Fixes: 64914da24ea9 ("drm/fbdev-helper: don't force restores") Cc: Noralf Trønnes Cc: Thomas Zimmermann Cc: Daniel Vetter Cc: Maarten Lankhorst Cc: Maxime Ripard Cc: David Airlie Cc: Daniel Vetter Cc: dri-devel@lists.freedesktop.org Cc: # v5.7+ Cc: Bartlomiej Zolnierkiewicz Cc: Geert Uytterhoeven Cc: Nathan Chancellor Cc: Qiujun Huang Cc: Peter Rosin Cc: linux-fbdev@vger.kernel.org Signed-off-by: Daniel Vetter Reviewed-by: Alex Deucher --- drivers/gpu/drm/drm_fb_helper.c | 63 +++++++++++++++++++++++++------- drivers/video/fbdev/core/fbcon.c | 3 +- include/uapi/linux/fb.h | 1 + 3 files changed, 52 insertions(+), 15 deletions(-) diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c index 170aa7689110..ae69bf8e9bcc 100644 --- a/drivers/gpu/drm/drm_fb_helper.c +++ b/drivers/gpu/drm/drm_fb_helper.c @@ -227,18 +227,9 @@ int drm_fb_helper_debug_leave(struct fb_info *info) } EXPORT_SYMBOL(drm_fb_helper_debug_leave); -/** - * drm_fb_helper_restore_fbdev_mode_unlocked - restore fbdev configuration - * @fb_helper: driver-allocated fbdev helper, can be NULL - * - * This should be called from driver's drm &drm_driver.lastclose callback - * when implementing an fbcon on top of kms using this helper. This ensures that - * the user isn't greeted with a black screen when e.g. X dies. - * - * RETURNS: - * Zero if everything went ok, negative error code otherwise. - */ -int drm_fb_helper_restore_fbdev_mode_unlocked(struct drm_fb_helper *fb_helper) +static int +__drm_fb_helper_restore_fbdev_mode_unlocked(struct drm_fb_helper *fb_helper, + bool force) { bool do_delayed; int ret; @@ -250,7 +241,16 @@ int drm_fb_helper_restore_fbdev_mode_unlocked(struct drm_fb_helper *fb_helper) return 0; mutex_lock(&fb_helper->lock); - ret = drm_client_modeset_commit(&fb_helper->client); + if (force) { + /* + * Yes this is the _locked version which expects the master lock + * to be held. But for forced restores we're intentionally + * racing here, see drm_fb_helper_set_par(). + */ + ret = drm_client_modeset_commit_locked(&fb_helper->client); + } else { + ret = drm_client_modeset_commit(&fb_helper->client); + } do_delayed = fb_helper->delayed_hotplug; if (do_delayed) @@ -262,6 +262,22 @@ int drm_fb_helper_restore_fbdev_mode_unlocked(struct drm_fb_helper *fb_helper) return ret; } + +/** + * drm_fb_helper_restore_fbdev_mode_unlocked - restore fbdev configuration + * @fb_helper: driver-allocated fbdev helper, can be NULL + * + * This should be called from driver's drm &drm_driver.lastclose callback + * when implementing an fbcon on top of kms using this helper. This ensures that + * the user isn't greeted with a black screen when e.g. X dies. + * + * RETURNS: + * Zero if everything went ok, negative error code otherwise. + */ +int drm_fb_helper_restore_fbdev_mode_unlocked(struct drm_fb_helper *fb_helper) +{ + return __drm_fb_helper_restore_fbdev_mode_unlocked(fb_helper, false); +} EXPORT_SYMBOL(drm_fb_helper_restore_fbdev_mode_unlocked); #ifdef CONFIG_MAGIC_SYSRQ @@ -1318,6 +1334,7 @@ int drm_fb_helper_set_par(struct fb_info *info) { struct drm_fb_helper *fb_helper = info->par; struct fb_var_screeninfo *var = &info->var; + bool force; if (oops_in_progress) return -EBUSY; @@ -1327,7 +1344,25 @@ int drm_fb_helper_set_par(struct fb_info *info) return -EINVAL; } - drm_fb_helper_restore_fbdev_mode_unlocked(fb_helper); + /* + * Normally we want to make sure that a kms master takes + * precedence over fbdev, to avoid fbdev flickering and + * occasionally stealing the display status. But Xorg first sets + * the vt back to text mode using the KDSET IOCTL with KD_TEXT, + * and only after that drops the master status when exiting. + * + * In the past this was caught by drm_fb_helper_lastclose(), but + * on modern systems where logind always keeps a drm fd open to + * orchestrate the vt switching, this doesn't work. + * + * To no break the userspace ABI we have this special case here, + * which is only used for the above case. Everything else uses + * the normal commit function, which ensures that we never steal + * the display from an active drm master. + */ + force = var->activate & FB_ACTIVATE_KD_TEXT; + + __drm_fb_helper_restore_fbdev_mode_unlocked(fb_helper, force); return 0; } diff --git a/drivers/video/fbdev/core/fbcon.c b/drivers/video/fbdev/core/fbcon.c index 9d28a8e3328f..e2a490c5ae08 100644 --- a/drivers/video/fbdev/core/fbcon.c +++ b/drivers/video/fbdev/core/fbcon.c @@ -2402,7 +2402,8 @@ static int fbcon_blank(struct vc_data *vc, int blank, int mode_switch) ops->graphics = 1; if (!blank) { - var.activate = FB_ACTIVATE_NOW | FB_ACTIVATE_FORCE; + var.activate = FB_ACTIVATE_NOW | FB_ACTIVATE_FORCE | + FB_ACTIVATE_KD_TEXT; fb_set_var(info, &var); ops->graphics = 0; ops->var = info->var; diff --git a/include/uapi/linux/fb.h b/include/uapi/linux/fb.h index b6aac7ee1f67..4c14e8be7267 100644 --- a/include/uapi/linux/fb.h +++ b/include/uapi/linux/fb.h @@ -205,6 +205,7 @@ struct fb_bitfield { #define FB_ACTIVATE_ALL 64 /* change all VCs on this fb */ #define FB_ACTIVATE_FORCE 128 /* force apply even when no change*/ #define FB_ACTIVATE_INV_MODE 256 /* invalidate videomode */ +#define FB_ACTIVATE_KD_TEXT 512 /* for KDSET vt ioctl */ #define FB_ACCELF_TEXT 1 /* (OBSOLETE) see fb_info.flags and vc_mode */